Ive been followiung the game dev logs and there will only be 3 races and it will be a story based campaign. Eldar, space marines and tyranids.Also the game is not going to be a full army rts. A good Q&A was done by Gamespot. Gives some interesting insight on the new gameEven though the game is story driven you do still get to choose what planets to travel to next to try and save from the nids.